Prof. Lei Wang
Department of Chemcal and Biomolecular Engineering, National Unversity of Singapore
Lei Wang completed his doctorate at KTH Royal Institute of Technology in 2015, where he studied water oxidation based on molecular catalysts. In 2016, he joined Stanford University as a Wallenberg-Stanford postdoc fellow and worked on electrochemical CO reduction. He began his current position at National University of Singapore at the end of 2020. He has published over 50 peer reviewed scientific papers in international journals and received over 4000 citations with an H-index of 32. He was awarded as NRF Fellow in Singapore in 2021. His current research focuses on catalyst discovery and understanding reaction mechanisms for electrochemical CO2 reduction.
Electrochemical CO2 reduction offers exciting opportunities in turning the waste carbon into value-added chemicals/fuels. Among different CO2 reduction products, formate has attracted particular interest, as it shows promising near-term economic feasibility. Pd-based electrocatalysts have demonstrated excellent selectivity towards formate production, however, only within a narrow potential window of 0 V to -0.25 V vs. RHE. It has shown that Pd-based electrocatalysts suffer from the potential-dependent deactivation pathways (α-PdH to β-PdH phase transition, CO poisoning, etc.) and quickly loss their activity towards formate production. Thus, it is desirable to establish new strategies to enable Pd-based CO2 reduction over a broader potential window to achieve both energy efficient and practical relevant formate production.
In this work , we discovered that polyvinylpyrrolidone (PVP) ligand decorated Pd surface exhibits an unexpected promotion effect on CO2 electroreduction. Specifically, PVP decorated Pd can afford selective formate production at a much-extended potential window (beyond -0.7 V vs. RHE) with significantly improved activity (14-times enhancement at -0.4 V vs. RHE) compared to that of the pristine Pd surface. Combined results from physical/electrochemical characterizations, kinetic analysis and first principal simulations suggest that the PVP capping ligand can effectively stabilize the Pd species with high valence state (Pdẟ+) resulted from the catalyst synthesis and pretreatments, and these Pdẟ+ species are responsible for the inhibited phase transition of α-PdH to β-PdH, as well as the suppression of CO and H2 formation. Overall, our study confers a desired catalyst design principle: introducing positive charges into Pd-catalysts to enable efficient and stable CO2 to formate conversion.
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